1. Field of the Invention
The invention relates to a piston engine in which an actuating fluid space is filled with an actuating fluid.
2. Description of the Related Art
Recent years have witnessed growing interest in Stirling engines, which have excellent theoretical thermal efficiency, for recovering waste heat from internal combustion engines installed in cars, buses, trucks and the like, and also waste heat in factories. Stirling engines, which are a kind of piston engine, have an actuating fluid space filled with a high-pressure actuating fluid. For instance, Japanese Patent Application Publication No. 2006-348893 (JP-A-2006-348893) discloses a Stirling engine in which the interior of a crankcase is pressurized.
The actuating fluid space of the Stirling engine is filled with an actuating fluid, and hence the Stirling engine cannot start up unless the piston moves reciprocally by being acted upon by a force that is greater than the maximum pressure of the actuating fluid. The interior of the crankcase of the Stirling engine disclosed in JP-A-2006-348893 is pressurized, and hence the pressure of the actuating fluid in the actuating fluid space is accordingly high. This is problematic in that, as a result, substantial torque is required for starting the Stirling engine, and there must be provided some start means having significant torque for starting the Stirling engine. This entails considerable wastes.